Hardening photographic materials



ieatures hereinafter fully described,

ing indicative however,

principle of the invention .such as sodium thiosulphate,

Patented Sept. 30, 1941 UNITED STATES PATENT" OFFICE v nsansmc mo rfgsrmo m'rsams William H. Wood, Bediord, Ohio,

llarris-seybold-l'otter Company,

asslgnor to Cleveland.

Ohio, a corporation of Ohio No Drawing. Application June 16, 1939 Serial No. 219,514

7 Claims. (CI. 95-88.)

For hardeningrthe gelatin of photographic plates, films and papers, it is customary to employ a chromium salt such as potassium chromium sulphate, known as potassium chromium alum, together with sulphuric acid or acetic acid, and in some cases the sulphuric or acetic acid is used with an aluminum salt such as potassium aluminum sulphate or alum, and these A formed also an insoluble preeipitate which not only reduces the hardening eiIect but occasions a hard scum or deposit on the photographic material and on the walls of thevessel, particularly when the hardener is ineorporated in or is sodium thiosulphate terioration there is fixing solutions. In accordance with the present invention, it now becomes possible to avoid the disadvantages noted, and new hardening solutions may be provided which operate especially desirably.

To the accomplishment otthe foregoing and related ends, the invention, then, comprises the and particin the claims, the following forth in detail certain illusthe invention, these beof but a few or the variularly pointed out description setting trative embodiments 01 ans ways inwhichthe may be employed. 1 I

I have found that hardening solutions prepared :according to my invention maintain their hard- ,ening effect over extended periods, and tendency to over {hardening is absent, and the hardening solutions of my invention may be used separately or maybe incorporated in a silver halide solvent and when such sodium 'thiosulphate is present the advantages of the invention are notably apparent. My hardening composition involves gluconic acid, by'

and on the other hand solutions of this those containing potassium used in conjunction with material to be hardened'oon- I which term I include glucono-delta-lactone and glucono-gamma-lactone, itbeing commonly understood that the two latter compounds when dissolved in water hydrolyze to form gluconic acid. The normal gluconic acid may be used, or generally I prefer to employ the lactone form because of its solid state instead of liquid and its general availability and convenience. of the two lactones I prefer the delta lactone because oi its relative cheapness. The gluconic acid or glucono-lactone may be employed in concentrations or diflerent amounts depending upon the particular conditions to be met and the results sought,

. and in general it may be such as to yield 0.5 to

15 per. cent of gluconic acid in the solution: and therewith I employ a hardening salt, such as ordinary alum or chrome alum i. e. potassium aluminum sulphate or potassium chromium sulphate, and generally I prefer the chromium salt, as the eil'ect is more permafient.

As an example of a bath tor hardening only,

the following may be noted:

Water. 0 cc 1000 Glucono-delta-lactone grams 5 Potassium aluminum sulphatedo- 20 b 1:: another example of this kind of hardening wilt! or Glucono-delta-lactone .......;.-.....'grams.. 5 Potassium chromium sulphate ..do 20 As an example of a combined hardening and fixing bath, the following may be noted: V

water cc Glucono-delta-lactone --grams Potassium aluminum sulphate ..;.do......- 20 Sodium thiosulphate do 400 Sodium sulphite -..do 20 Ammonium chloride -do..- 50

As another example:

Water 50o Glucono-delta-iactone --grams. 50 Potassium chromium sulphate -do 20 Sodium thiosulphate do 400 Sodium sulp do 20 Ammonium chloridedo 50 Other modes oi applying the principle of the invention may be employed, change being made as regards the details'described, provided the teatures stated in any of theiollowing claims, or the equivalent oi such, be employed.

2 ass-Lao I thereiore particularly point out and dis- 5. A treating composition for 'tinctly claim as my invention: gelatin layers carrying a silver image containing 1. In a process of the character described. suba substance selected from the group conic acid containing 0.5 to 15 per cent oi giugluconic acid insoiution and therewith a fixing conic; acid and a chromium salt and a fixing agent and a hardening agent selected from the agen Y 2. In a process of the character described, subchromium salt having hardening action.

Jecting a photographic gelatin layer carrying a 10 6. A treating composition for photographic silver image to the action '0! a solution glngelatin layers carrying a silver image containing conic acid containing 0.5 to 15 per cent of glua substance selected from,the group consisting subjecting a photographic gelatin layer carrying 15 gluconic acid .in solution and therewith a fixing gluconic acid containing to per cent of action. Y gluconic acid and an alum. 7. A treating bath for photographic gelatin gelatin layers carrying a silver image contain- 15 per cent of gluconic acid in solution and a ing a substance selected from the group consisthardening agent selected from the group conconcentration as to yield 0.5. to 15 per cent of having hardening action.

v gluconic acid in solution and therewith a harden- Q ing agent selected from the group consisting of WILLIAM H. WOOD. an aluminum salt and a chromium salt having hardening action. 1 r

Jecting a photographicgelatin layer carrying a of gluconic acid and glucono-lactone in suchv silver image to the action of a solution oi glu- 5 concentration as to yield 0.5 to 15 per cent of group consisting of an aluminum salt and a V conic acid and a chromium salt. .oi gluconic acid and glucono-lactone in such j 3. In a process of the character described, a concentration as to yield 0.5 to 15 per cent of 7 a silver image to the action of a solutionv of agent and a chromium salt having hardening 4. A treating composition for photographic layers carrying a silver image containing 0.5 to

ing of gluconio acid and glucono-lactone in such sisting of an aluminum salt and a chromium salt 7 

